Hi,I just finished the build of a 3D printer - based on the Prusa MK2 with all parts bought as cheap as possible from China. The frame and filament holder was of cause cut on my CNC machine. There was some interesting learning in terms of parts which can be used on the bookbuild or any custom variation you might build.

* Endstop Mechanical Limit Switches 3D Printer Switch for RAMPS 1.4 (circuitry for de-bouncing) are about $0.45* The MEGA 2560/ Ramps 1.4 board can be used for a CNC machine since there is a CNC firmware out there - it might be worth testing since it's $10 or less and replaces the need of a PC and the parallel interface - of cause you still need decent motor drivers.